Hygrostat



Patented July 12, 1932 UNITED STATES PATENT OFFICE MORTON O. SNEDIKER, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE POWERS REGULATOR COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS HYGROSTAT Application filed June 10,

My invention relates to hygrostats and particularly to a novel construction adapted to insure relatively very close regulation of the moisture content of air within a space.

It is common to utilize a moisture-sensltive element adapted to control an admission valve for moisture in the form of steam or water spray. However, due to the relatively slow action of the hygrostat and the speed 101 with which changes may be made in the moisture content of air, close regulation has been found to be diificult of attainment.

An object of the invention here disclosed is to provide for fine regulation without the use of unusually finely adjusted instruments. The result is accomplished by utilizing the hygrostat as a relay in the usual manner and by providing for balancing the forces as between the moisture-sensitive element and the relay air pressure, thus securing a condition that results in extreme sensitiveness.

My invention will be more readily understood by reference to the accompanying drawing, in which:

Fig. 1 is a plan view, somewhat diagrammatic in character, illustrating an installation of a hygrostat constructed in accordance with my invention, and

Fig. 2 is a side elevation, partly in section on the line 22 of Fig. 1. r

In the drawing I have illustrated a hygro- -stat having a base member 10, on which is mounted a moisture-sensitive element 11. This element is composed of a material that is expansive under the action of moisture, regulation being efiected by means of the screw 12 and the annular dial 13. l

The forward end of the element carries a thrust member 14 that abuts a pin 15 carried on the short or primary arm 16 of a bell crank lever. This lever is fulcrumed at 17 on the base, the upper extremity of the primary arm providing means for connection of tension springs 18 that tend to oppose the expansive action of the element.

The other arm 19 of the bell crank projects substantially horizontally parallel to the base and has an opening 20 therein which surrounds a projection 21 carrying a leak port 30. A valve member 22 controls the leak lever 19.

1931. Serial No. 543,378.

port, a light spring 23 tending to seat the valve, supplementing the action of gravity if the device is mounted in a horizontal position. The spring is supported against a lateral arm 24 carried on a post 25 fixed to the 5 base. Air under pressure admitted through the pipe 26 is conducted through a passage 27 to a restriction screw indicated in general by a bolt head 28 and from thence through the passage 29 to the leak port 30. From the 1.0 leak port, the passage continues as at 31 to a chamber 32, the upper wall of which is constituted by a diaphragm 33. A passage 34 from the chamber 32 leads to the pipe 35 and thence to a bellows-operated valve member as 36 or other instrumentality for controlling the admission of moisture tothe controlled space. An adjusting screw 37 mounted in the long arm 19 at a point near its extremity contacts against the diaphragm 33.

The operation is as follows: With the parts in the positionshown in the drawing, the valve 22 is slightly open permitting escape of air sufiiciently to prevent the building up of sufiicient pressure in the pipe 35 to actuate .76 the valve 36. With an increase in moisture a slight expansion of the moisture-sensitive element will take place, thus oscillating the bell crank, seating the valve 22 and slightly depressing the diaphragm 33. This results in the building up of pressure in the air line and the chamber 32 beneath the diaphragm and tending to lift the diaphragm and the As the expansible moisture-sensitive element is, under. the conditions described, practically incompressible, a slight bending action takes place in the arm 19 tending to again unseat the valve 22. However, as the moisture-sensitive element continues to expand apoint is soon reached where the tendency to close the valve is balanced by the tendency to open it, and pressure accumulates in the air line suflicient to actuate the operating valve and to change the rate of discharge of moisture. After fluctuation above and below the predetermined moisture content when the instrument is started in operation, a balance is soon reached where the slightest change in the moisture content of the air will be reflected in a change of adjust- I00 ment of the controlling valve, and this will continue indefinitely.

Of course, on a reversal of conditions, a reversed operation will take place and I have not specifically described it. It Will be understood that I have described and shown only the one type of air actuated controlling valve, that is, the type in which the valve is closed by an accumulation of pressure in the relay system. The opposite operation is also contemplated. r

The reason for the accurate operation of the described apparatus may be attributed to the relative resiliency of the bell crank arms enabling a sensitive balance of pressures to be arrived at. This result may be secured in other ways, and I do not wish to be limited except as indicated in the appended claims.

I claim:

1. In a hygrostat, the combination ot a moisture-sensitive element, a bell crank having primary and secondary arms, the primary arm being in contact with said element, means providing an air passage for controlling valve means to regulate the admission of moisture, a leak valve in said passage adapted to be actuated by the secondary arm of said bell crank, and a diaphragm open on one side to air pressure in said passage, said diaphragm acting on the secondary arm of said bell crank and ten ding to oppose the action of the moisture-sensitive means,-the relative flexibility of said secondary arm being such as to permit of slight actuation of said leak valve in opposition to the action of the moisturesensitive means.

2. In ahygrostat, the combination of a support, an eXpansible moisture sensitive element mounted thereon, a bell crank mounted for oscillation on the support, said bell crank having primary and secondary arms, said primary arm being adapted to be moved by the thrust of said moisture-sensitive element, means providing a restricted air passage in said support, a leak valve in said passage in position to be actuated by the secondary arm of the bell crank, and an expansible member adapted to be affected by pressure in said air passage, said expansible member being in contact with the secondary arm of the bell crank near its extremity, the length and flexibility of said secondary arm being such as to permit movement of the leak valve by the action of said expansible member in opposition to the action of the moisture-sensitive means.

3. In a hygrostat, the combination of a support, a moisture-sensitive expansible element mounted on said support, means for effecting adjustment of said element, an angular lever having a fulcrum on said support and provided with a short primary arm and a relatively long secondary arm, an air passage in said support, a leak valve in said passage, said valve being in position to be moved to open or closed position by the secondary arm,

and a diaphragm in the air passage, said diaphragm acting on said secondary arm at a point near its extremity.

4:. In a hygrostat, the combination of a base, a moisture-sensitive member mounted thereon, a lever fulcrumed on said base, said lever having relatively long and short arms, the short arm being in contact with the moisture-sensitive element, means providing an air passage in said base, means for adj ustably restricting said passage, a leak valve in said passage, said valve being adapted to be actuated by the long arm of said lever, and a diaphragm open on one side to the air in said passage, said diaphragm acting on the long arm of said lever at a point near the extremity thereof.

In testimony whereof I have afiixed my signature.

MORTON O. SNEDIKER. 

